“…One of the most widely used safety metrics of TCT is the Time-To-Collision (TTC) ( Laureshyn et al, 2016 , Mahmud et al, 2019 , Wang and Stamatiadis, 2014 ). Using TTC, different traffic states can be identified in the famous NGSIM database ( Kovvali et al, 2007 ), with the states shown to correspond to different levels of risk ( Zhao et al, 2018 ). The potential risk for human drivers in dangerous car following situations can be assessed ( Liu et al, 2019 ).…”